As noted above, this invention relates to an exhaust control device for an engine, and more particularly to an improved device for controlling the exhaust gases in a multiple cylinder engine so as to improve the performance of the engine throughout the entire speed and load ranges.
As is noted in the aforesaid co-pending applications of Hideaki Ueda, Ser. Nos. 935,340 and 935,342, it has been found that the configuration and design of an exhaust system for a multiple cylinder engine can have a significant and profound effect on the engine's performance curves. For example, under some running conditions, the exhaust gases from one cylinder may interfere with the flow of exhaust gases from another cylinder and substantially reduce the performance under mid-range conditions, even though the system is designed to provide good performance under high speed conditions. It has been found that the performance of the engine can be significantly improved by employing a valve or reflective device in the individual exhaust pipes leading from the respective exhaust ports and which is controlled in response to engine running conditions so as to avoid the interference which might otherwise be caused from the exhaust pulses from one cylinder interrupting with the exhaust flow from another cylinder. In connection with providing such control, it is desirable if each exhaust pipe is supplied with its own individual exhaust control valve in order to avoid the aforenoted dilatorious effects. However, when providing such multiple exhaust valves, there are substantial difficulties in providing a compact construction and also one which will not be adversely affected by the high temperatures of the exhaust gases.
In addition to the foregoing purpose, such exhaust control valves may be employed for generating a self E.G.R. (exhaust gas recirculation) effect to improve exhaust gas emission control.
It is, therefore, a principal object of this invention to provide an improved exhaust control device for an engine.
It is a further object of this invention to provide an improved control valve for controlling the exhaust gases of multiple exhaust pipes of a multiple cylinder internal combustion engine.
It is a further object of the invention to provide an improved, compact control valve for the exhaust gases of an engine wherein the effects of heat on the valve are substantially minimized.
Of course, it is possible to design a control valve wherein one shaft is rotatably journaled in a common valve body and supports a plurality of valves for controlling the flow through the respective exhaust passages. However, the provision of such a long control shaft presents problems in connection with heat effects. That is, the thermal expansion of a long shaft will be greater than that of a short shaft and, accordingly, certain problems can result in connection with such single shaft arrangements. If multiple shafts are employed, the construction must be such that the shafts can be conveniently interrelated for movement, and the resulting valve body must still be compact in construction.
It is, therefore, a still further object of this invention to provide an improved exhaust control device for engines having multiple interconnected shafts in a single valve body.
Although engines embodying exhaust control devices for improving their performance may find application in a wide variety of vehicles, one type of vehicle in which such devices are particularly useful is a motorcycle. In connection with motorcycles, one common configuration places the cylinders of the engine in a transversely disposed relationship, and the exhaust pipes from the cylinders extend forwardly, downwardly, and then pass beneath the engine before discharge to the atmosphere. With such an arrangement, the exhaust control device may frequently be positioned beneath the engine, and thus it can significantly effect the ground clearance, both when traveling in a straight ahead direction and also when cornering wherein the rider normally leans the motorcycle to assist in turning. However, if the control valve has any substantial transverse dimension, it can seriously interfere with the amount of leaning which can be accomplished by the rider.
It is, therefore, a still further object of this invention to provide an improved, compact exhaust control valve for a vehicle which will have a compact configuration and which can be placed beneath the engine of a vehicle such as a motorcycle.